Chemically treated wood pulp and a method of producing a cellulosic product



Patent ed Oct. 19, 1948 r CHEMICALLY TREATED WOOD PULP AND A METHOD OFPRODUCING A CELLULOSIC PRODUCT Paul Henry Schlosser and Kenneth RussellGray, Shelton, Wash, assignors to Rayonier Incorporated, Shelton, Wash.,a corporation of Delaware No Drawing. Application November fi, 1944,Serial No. 562,262

14 Claims. (Cl. 106-163) This invention relates to the production ofcellulosic products and has for its general object the provision ofcertain improvements in carrying out one or more of the processing stepsused in the production of such products. The invention aims particularlyto improve the emulsification or dispersion of opacifying agents in thespinning solution, and to suppress the formation of incrustations,sometimes referred to as craters, formed in spinneret orifices. Theinvention further contemplates, as a new article of manufacture, achemically prepared wood pulp product having incorporated therein .amixed ether containing a polyalkylene oxide radical and a substitutedaryl hydrocarbon radicaL' In one of its important aspects, the inventioninvolves the use of chemically prepared wood pulp as a source ofcellulose in the preparation of cellulosic solutions for the viscose andother processes in which extruded regenerated cellulose is produced, andhas for a particular object the use of the said mixed ethers to improveeither or both the emulsification and spinning.

The invention is especially applicable to the spinning of viscose rayonin which chemically prepared wood pulp (hereinafter called wood pulp) isused as a source of cellulose and the invention will be described withreference to that process, it being understood that it is alsoapplicable to other processes where aqueous cellulosic solutions areopacified or extruded into filaments or films.

Wood pulp as usually prepared as a source of cellulose for the viscoseand related spinning in dustries is of various degrees of purity, and isgenerally supplied for use in the form of sheets. Normal dissolving woodpulp in present use consists mainly of cellulose and containsanappreciable amount of non-cellulosic impurities, such ashemi-celluloses, fats, resins, waxes, etc. One of the main objects inthe manufacture of highly refined dissolving pulp is to remove as muchas possible of the non-cellulosic impurities so that a whiter, purerpulp results which is capable in the manufacturing of rayon of producinga higher grade yarn. y

We find, however, that not all of the non-cellulosic impurities whichcan be removed are undesirable, and in fact certain of such impurities,normally present in small amounts, are highly beneficial as regards thestep of emulsifying or dispersing oils or pigments in the viscose. Thesebeneficial impurities which aid the step of emulsiilcation are probablyfor the most part surfaceactive materials of the anion active class ormaterials which can give rise to the production of such surface-activematerials during the processing of pulp into viscose. In a pulp whichhas not been highly refined most of these beneficial impuritiesconstitute a portion of the materials removed by organic solvents, asfor example ether, benzene, alcohol, et cetera. These beneficialimpurities, often loosely termed resins," are mainly of the nature ofwaxes, fats, and resins, the latter often being present in a relativelysmall amount.

Furthermore, we find that there are impurities present in pulp which hasnot been highly refined which have marked effects, both favorable andadverse, on the formation of incrustations in the orifices of thespinnerets during spinning. In theory, the problem of making a good pulpcould be solved by removing all the undesirable impurities includingdegraded cellulose and non-cellulosic carbohydrates while retainingthose impurities which facilitate the steps of emulsification andspinning. In practice such a clean-cut separation is difiicult toaccomplish directly. We have discovered that better results areobtainable by removing most or all of the impurities, including thosewhich serve beneficially as regards the emulsification step and thosewhich affect spinning, either positively or negatively, and then causingto be present in the viscose, materials of a class entirely differentfrom the natural impurities originally present, and which greatly aidsteps of emulsification and spinning.

White, highly purified or refined wood pulps are very advantageous forthe production of high grade rayon yarns of superior strength and color,and for this reason, are highly esteemed by the trade. Such highlyrefined pulps are in general characterized by having an ether extractlower than 0.15% where such values refer to the amount of natural etherextractable material left in the pulp after the purification processes.While our invention is particularly applicable to such high- 1y refinedpulp containing not more than 0.15% of ether extractable material, itmay be applied with certain advantages to the processing of normaldissolving pulps containing more than 0.15% of ether extractablematerial, although such pulps do not generally yield the highest gradeyarns and their emulsification with oils is not usually accompanied byan great difficulty.

In accordance with the invention a small quantity of a mixed ethercontaining a polyalkylene oxide radical, and a substituted arylhydrocarbon radical (as hereinafter more particularly described), isincorporated in the materials used in producing the cellulosic solutionprior to releast one cycloalkyl radical.

The mixed ethers of the invention are at least dispersible in water andpreferably substantially soluble in water. For reasons of dispersibilitythe polyaikylene oxide radicals in the mixed ethers of the invention arederived from the first two members of the 1-2 alkylene oxides. Thesemembers are ethylene oxide and propylene oxide, or in other words, the1-2 alkylene oxides having up to 3 carbon atoms.

' Structurally the mixed ethers of the invention have the formula:

where R is an aryl radical substituted by at least one aliphatic alkylor acyl radical having more than two carbon atoms or by at least onecycloalkyl radical where R1 is hydrogen or methyl, and where a: is awhole number greater than 1.

In view of its higher solubilizing effect a polyethylene oxide chain isthe preferred form for the polyalkylene oxide radical. Preferably thepolyethylene oxide chain will have from 5-25 ethenoxy residues.Practically it is believed there is no upper limit for the number ofethenoxy groups in the polyethylene oxide radical. Materials with apolyethylene oxide group containing even about 160 ethenoxy groups maybe satisfactorily used.

While the mixed ethers used in our invention are preferablysubstantially water soluble, it is possible to obtain the advantages ofthe invention in part using compounds of only slight solubility. Thus,mixed ethers containing even the simplest possible polyethylene oxideradical composed of two ethenoxy groups, may be used. Even though suchproducts do not have a great solubility they still possess a suflicienttendency to emulsify so that they may be dispersed in a finely dividedstate in the viscose yielding in part the advantages of the invention.If, however, a high degree of solubility in water is desired with suchagents, as for example, in the preparation of concentrated stocksolutions for application to the pulp or in the viscose process, it maybe advantageous to combine them with dispersing agents. Such additionaldispersing agents should preferably be of a non-ionic nature, forexample, a. mixed ether of polyethylene oxide containing a, higherproportion of ethenoxy groups. In the preferable form of our invention,however, suflicient ethenoxy groups will be present in the polyethyleneoxide radical so that the products will be substantially water solubleor dispersible without the aid of any additional dispersing agents.

The preferred compounds for use in the invention are mixed etherscontaining a polyethylene oxide radical and an alkaryl radical in whichthe aryl group is substituted by at least one alkyl radical with morethan two carbon atoms.

Further from the standpoint of improving emulsiflcation, the mostpreferred class of materials are mixed ethers containing a polyethyleneoxide radical and an alkyl phenyl hydrocarbon radical having at leastone substituted alkyl radical with 3-30 and especially from 7-20 carbonatoms. In the very best cases of all the phenyl radical will besubstituted by only a single alkyl radical of 7-20 carbon atoms. Forbest results the polyethylene oxide radical will have from 5-25 ethenoxyresidues. Such compounds are also particularly effective in suppressingincrustations in spinneret orifices during spinning.

The mixed ethers of the invention may be prepared from substitutedphenols by any of the known methods for reacting ethylene oxide orpropylene oxide with a phenol. They may also be prepared by etherifyingsubstituted ph nols with polyalkenoxy glycols, as, for example, byreacting the sodium salt of a substituted phenol with a halogen hydrinof the polyethylene glycol. The substituted phenols may also be reactedwith mixtures of ethylene oxide and propylene oxide or with one of thesematerials following use of the other.

We prefer, however, to react ethylene oxide at moderate temperatureswith a substituted phenol (in the most preferred cases with analkylation product of phenol itself), incorporating an alkali ascatalyst with the phenol. In practice the products will usually bemixtures having some variation in the length of the polyethylene oxidechains but the products are quite satisfactory to use for the purpose ofthe invention in the form of such mixtures.

Again when the alkaline catalyst used consists of a small amount ofaqueous caustic soda (e. g., 48% NaOH) all of the ethylene oxide willprobably not be consumed in extending the length of the polyether chainon the substituted phenol but a portion (in view of the small amount ofwater present) will be consumed with the formation of polyethyleneoxide. The presence of polyethylene oxide is, however, not harmful toour invention.

Instead of reacting ethylene oxide with the substituted phenols, theirglycol ethers may be used since these would be initial products in theformation of the polyether chains.

. In condensing ethylene oxide with a substituted phenol it is quitesatisfactory to base the desired molar ratio on the assumption that theentire weight of ethylene oxide will react to form polyether chains onthe phenol, homogeneous as to length. This may be done since smallvariations in the ratio of ethenoxy do not produce very greatdifierences in the properties. Furthermore, it is not necessary to useexact stoichiometrical proportions of ethylene oxide. Thus, for example,if pure p-diisobutyl phenol were treated with 12.5 moles of ethyleneoxide, mixtures of mixed ethers would be obtained in which chains of 12and 13 ethenoxy groups would predominate.

Again it is not necessary to use pure substituted phenols. Thus evenwhile a single substitutin alkyl of more than two carbon atoms is mostpreferred, actually such an intermediate for mixed ether preparation maypractically contain as well as the predominating mono-alkyl phenol,small amounts of dior poly-substituted as well as unsubstituted phenol.

After completionof the reaction with ethylene oxide the reactionproducts may be used directly if they are to be added to the viscose.Where, however, alkali has been used as catalyst and the products are tobe added to the pulp the residual alkali should be neutralized in anyconvenient manner-as for example, by 30% H2804 or concentrated HCl. Forthe purposes of our invention frequently no further purification will belie-- quired. Where an extremely light-colored proddrying anddecolorizing the benzene solution by addition of sodium sulphate anddecolorizing charcoal. After filtering, the product was isolated byevaporating of! the benzene, finally applying vacuum.

The alkyl, acyl or cycloalkyl substituted phenols used for preparing themixed ethers can be readily prepared by the methods known to the art. Byphenols is meant not just phenol itself but all monohydroxy substitutionproducts of aromatic hydrocarbons. The alkyl or acyl groups may bebranched or straight chain in character. Fbr practical reasons-the alkylphenols having from 3-30 carbon atoms in thealkyl group and especiallyfrom 7-20 carbon atoms are preferred. Also the introduction of branchedrather than straight chain alkyls into the phenols will in most cases bemore practical. This is not only because in many cases the alkyl oralkylene compounds reacted with the phenol will be of a secondary ortertiary character or at least of a branched chain structure. Actuallyeven in many cases where normal primary alkyi compounds are reacted withphenols the result will still be the introduction of a branched chainrather than a straight chain alkyl.

Substituted phenols may be used for the preparation of mixed ethersirrespective of the position of the substituted alkvl, cycloalkyl' oracyl group. Thus in the case of a monocyciic phenol the substitutedgroup or groups may be m-, or pto the hydroxyl or as a mixture of these.Again with polycyclic phenols substituted products may be usedirrespective of the position of the substituting group. All thesubstituted phenols used, however, are monohydroxylic, i. e. they aresubstituted aryl hydroxides.

Phenols particularly useful for preparing substituted phenols for use asintermediates in the production of the mixed ethers of the invention arethose of the-benmne and naphthalene series. These are especially phenol,o, m, and p cresol, a and s naphthol and mixtures of these.

Methods of preparing the substituted phenols from the phenols (by whichterm is included phenol, cresols, xylenols, naphthols, etc.) include thereaction with the phenols of alcohols, alkyl halides or alkyl esters inthe presence of a suitable condensing agent. Another practicalwell-known method involves the addition of an olefine to the phenolusually in the presence of a catalyst. With phenol itself this usuallyresults in introduction of the alkyl in the para position to thehydroxyl. Examples of olefines which may be used are diisobutyleneisododecylene, etc.

It is not necessary to introduce pure alkyls into the phenols. Thusmixtures of oleflnes or of alkyl compounds may be reacted with thephenols. As an example of a suitable mixture of alkyl compounds may bementioned the use of chlorinated rinated hydrocarbons and generallyaveraging from 12-20 carbon atoms.

solving the neutralized product in benzene, and

The production of acyl substituted phenols may be accomplished by thewell-known Friedel-Crafts reactions.

As examples of mixed ethers which may be used in the invention are mixedethers of polyethylene oxide and the following phenols:

Alkyl phenols p-n-Bu'tyl phenol, 'p-tertiary butyl phenol,D-mmYn-tetramethyl butyl phenol, decyl phenol, dodecyl phenol, cetylphenol, octadecyl phenol, (2- ethyl heXyl) phenol, oleyl phenol, suchpolyalkyl phenols as di and trioctyl phenols, amyl cresol, dodecylcresol; substituted naphthols such as iso propyl naphthol, iso butylnaphthol, dodecyl naphthoi.

Cycloalkyl phenols p-Cyclohexyl phenol, cycl-ohexyl-cyclohexyl phenol,bomyl phenol.

Acyl phenols Butyryl, valeryl, dodecyl, stearoyl phenols and thecorresponding cresols, naphthols and xylenols. As previously stated themost preferred mixed ethers are those containing predominantly a monoalkyl phenyl radical. An example of such mixed ethers which areparticularly effective in kerosene fractions predominating inmonochloimproving emulsification and improving spinning are thoserepresented by the following formula:

CH: CH:

cm-d-cm-dOo 023.0 ,11

nection with any of the steps in producing re'generated cellulose, theyare especially beneficial when present in a spinning solution containingan opacifying or delustering agent, and when in contact with thespinneret due to their presence either in the spinning solution or inthe spin bath.

In the usual viscose process the sheets are first subjected to asteeping step to convert the cellulose to alkali cellulose, and thepressed sheets of alkali cellulose are then shredded to form a fiufiymass of fibers. The fluffy mass is xanthated, dissolved in dilutecaustic soda and the solution commonly known as viscose filtered toremove undissolved fibers and gel-like materials, and ripened to impartthe desired properties for satisfactory spinning.

When viscose rayon is delustered by incorporating a suitable opacifyingagent in the spinning solution, usually an oil or a pigment such astitanium dioxide, it is necessary in order to get a uniformemulsification or dispersion of the agent throughout the body of theviscose solution to use an emulsifying or dispersing agent. The mixedethers of the invention produce an exceptionally good emulsifying anddispersing efiect which is quite remarkable in view of the smallquantities used. The emulsification is characterized by the fineness,not only of the average particle size, but also by the uniformity ofsize so that the resulting viscose solution is substantially free ofeven small amounts of large globules which weaken the filaments onspinning.

Viscose solutions used in making rayon are preferred range of 5-20corporated either usually spun through metal spinnerets having that theyare in such contact with the metallic spinneret during spinning that theformation-of the craters is greatly minimized. The mixed ethers exertsuch a powerful influence on the materials present that only very smallquantities are necessary to accomplish the results sought. The extremelyeffective suppression of the craters is illustrated in some operationsby a reduction of from 80 to 95 per cent in the crater formation.

The mixed ethers may be incorporated in the wood pulp or at any stage ofthe viscose process. For treating the pulp, the compounds may be ininthe bulk pulp before sheet formation or in the sheets in any suitablestage as by spraying the pulp with an aqueous solution or dispersion ofthe compound, or by immersing in a solution or dispersion. A mostpractical and convenient method of I securing the presence of thedesired amount of mixed other is to incorporate the mixed ether in therefined wood pulp while it is on the sheet forming machine, as by meansof sprays or a rotating roll. In any case, there is produced a refinedpulp product having the compound incorporated therein. When the compoundis incorporated in the pulp, as by the manufacturer thereof, the pulpcomes to the rayon manufacturer in a form calculated to secure the fulladvantages of the invention in the preparation and processing of therefined pulp into rayon by the viscose process.

The mixed ethers, whether added to the spinning solution or to the pulp,come into direct contact with the orifices of the spinneret and suppressthe formation of incrustatlons on the walls of the orifices.

In order to efiect the contemplated improvements, the amount of thecompound used is relatively small, ranging from 0.01-0.20% on the bonedry weight of the pulp used. In most cases the preferred amounts forimproving spinning will generally be about 0.08-0.10.

As heretofore described, the mixed ethers and especially thosecontaining an alkyl phenyl group also bring about important improvementsin emulsification in that they give emulsions characterized not only byextraordinary fineness of particle size, but also by exceptionaluniformity of particle size and by exceptional stability in regard tomaintaining the particle size. The amount of the mixed ethers requiredfor securing the maximum improvement in emulsification is generallysomewhat less than the amount required for securing the contemplatedimprovement in suppressing or minimizing incrustation formation duringspinning. Thus the maximum improvement in emulsification will generallybe brought about by from 0.025%-0.05% of the mixed ether and the amountused for this purpose will commonly be about 0.03%. In order to securethe additional benefit of substantially suppressing or minimizingincrustation formation during spinning, the mixed ether should bepresent in amount of 0.08-0.10% or higher. By using such amounts ofmixed ether of the order of 0.08 0.10% the emulsions are substantiallyas fine and uniform as when using the' optimum of 0.025-

. 8 9.05%. Emulsions prepared, however, in the presence of the higheramount of mixed ether may under certain circumstances have a slighttendency to partially separate as a cream or scum during the variousviscose processing steps or during the aging period. Accordingly, whenboth emulsification and suppression of incrustations during spinning areof paramount concern, we prefer to add only 0.025-0.05% of a mixed ether(especially a mixed ether containing an alkyl phenyl group) but to stillobtain the contemplated improvement in cratering or an even greaterimprovement by adding an additional small amount of a cation-activeamino compound. In such cases the amount of the mixed ether willpreferably be about 0.03% and the amount of cation-active amino compoundwill preferably be about 005% though it may be added in amounts up to0.20%.

As two examples of products both of which are cation-active aminocompounds especially suitable for use in combination with the mixedethers as described above are (1) a mixture of the mono and diamides ofdiethylene trlamine and coconut fatt acids and (2) a reaction productconsisting substantially of mixed diethylene triamine diamides fromcoconut acids and a lower acid such as acetic acid.

So far as the objectives of the invention are concerned, there islittle, if any, improvement by increasing the amount of the mixed ethersabove 0.20% and such higher amounts frequently, give rise to certaindisadvantages. These disadvantages include the causing of excessivesoft. ness in the sheet, resulting in mechanical difliculties insteeping, excessive ball formation in xanthation, and difficulties inthe dissolvingoperation due to excessive foamingin the viscose solution.Also, there may be considerable difllculty in obtaining a completelydeaerated viscose which is necessary for satisfactory spinning. Higherconcentrations of the compound may also unduly lower the surface tensionof the viscose, thus changing the coagulating conditions so that theviscose cannot be satisfactorily spun by standard methods, causing thefilaments to break and the thread to stick to the godet wheels or threadguides.

While it is our preferred practice to incorporate the compound in thepulp, the presence of the compound during the processing steps ofopacifying and spinning may be secured in any other appropriate manner.However, we believe it will generally be found more advantageous toincorporate it in the pulp, both as a matter of convenience and economyin preparing and processing the viscose, and because a very uniformdistribution of the compound throughout the viscose is easily attained.The next best manner of obtaining very effective results is to spray theagents into the shredder prior to the completion of shredding. With themixed ethers containing alkyl phenyl radicals the method of adding theagents is of particular importance in regard to imparting 'anti-creamingproperties if the viscose is to be subsequently opacified. Whether thisis a question of the agents themselves undergoing some change during thexanthation or whether it is merely a question of the uniformity of thedistribution in the viscose, we do not know. In any event, for the mosteffective results the agents should be added not later than prior to thecompletion of shredding and preferably to the pulp prior to use in theviscose process.

This application is a continuation-in-part of following formula:

rated therein from 0.01 to 0.2 per cent by weight based on the bone dryweight of the pulp of a mixed ether having the following formula:

where R is an aryl radical substituted by at least one radical selectedfrom the class consisting of an alkyl radical with more than two carbonatoms, an acyl radical with more than two carbon atoms and a cycloalkylradical; where R1 is selected from the group consisting of hydrogen andmethyl and where .1: is a.whole number greater than 1.

2. As a new article of manufacture, a chemically prepared wood pulpproduct containing not more than 0.15 per cent ether extractablematerial and having incorporated therein from 0.01 to 0.2 per cent byweight based on the bone dry weight of the pulp of a mixed ether havingthe where R is an aryl radical substituted by at least one radicalselected from the class consisting of an alkyl radical with more thantwo carbon atoms, an acyl radical with more than two carbon atoms and acycloalkyl radical; where R1 is selected from the group consisting ofhydrogen and methyl and where a: is a whole number greater than 1.

3. The improvement in the production of regenerated cellulose productsby the viscose process from chemically prepared wood pulp whichcomprises incorporating in the viscose a mixed ether having thefollowing formula:

R- 0H0H10 H where R is an aryl radical substituted by at least oneradical selected from the class consisting of an alkyl radical with morethan two carbon atoms, an acyl radical with more than two carbon atomsand a cycloalkyl radical; where R1 is selected from the group consistingof hydrogen and methyl and where m is a whole number greater than 1.

4. The improvement in the production of regenerated cellulose product-sby the viscose process from chemically prepared wood pulp containing notmore than 0.15% ether extractable matter which is subjected to shredding'which ding the alkali cellulose a mixed ether having the followingformula:

where R is an aryl radical substituted by at least one radical selectedfrom the class consisting of an alkyl radical with more than two carbonatoms, an acyl radical with more than two carbon atoms and a cycloalkvlradical; where R1 is selected from the group consisting of hydrogen andmethyl and where .1: is a whole number greater than 1.

5. The improvement in the production of a regenerated cellulosic productfrom chemically prepared wood pulp by the viscose process whichcomprises adding to the pulp prior to use in the 10 viscose process amixed ether having the following formula:

RO(CHCH:O) n

where Ris an aryl radical substituted by at least one radical selectedfrom the class consisting of an alkyl radical with more than two carbonatoms, an acyl radical with more than two carbon atoms and a cycloalkylradical; where R1 is selected from the group consisting of hydrogen andmethyl 'comprises adding prior to completion of shredand where a: is awhole number greater than 1.

6. As a new article of manufacture, a chemically prepared wood pulpproduct having incorporated therein from 0.01 to 0.2 per cent by weightbased on the bone dry weight of the pulp of a mixed ether containing apolyethylene oxide radical with from 5-25 ethenoxy residues and an alkylphenyl radical in which the phenyl radical is substituted by an alkylradical with from 7-20 carbon atoms.

7. As a new article of manufacture, a chemically prepared wood pulpproduct containing not more than 0.15 per cent ether extractablematerial and having incorporated therein from 0.01 to 0.2 per cent byweight based on the bone dry weight of the pulp of a mixed ethercontaining a polyetheylene oxide radical with from 5-25 ethenoxyresidues and an alkyl phenyl radical in which the phenyl radical issubstituted by an ether containing a polyethylene oxide radical withfrom 5-25 ethenoxy residues and an alkyl phenyl radical in which thephenyl radical is substituted by an alkyl radical with from 7-20 carbonatoms.

9. The improvement in the production of a regenerated cellulosic productfrom chemically prepared wood pulp by the viscose process whichcomprises adding to the pulp prior to use in the viscose process a mixedether containing a polyethylene oxide radical with from 5-25 ethenoxyresidues and an alkyl phenyl radical in which the phenyl radical issubstituted by an alkyl radical with from 7-20 carbon atoms.

10. As a new article of manufacture,a chemically prepared wood pulpproduct having incorporated therein from 0.01 to 0.2 per cent by weightbased on thebone dry weight of the pulp of a mixed ether having thefollowing formula:

on; cHi' Hz 0 Ha on, em cm- E-cm-e-O0 (ozmomr CH5 CH3 where a: is awhole number from 5 to 25.

12. The improvement in the production of regenerated cellulose productsby the viscose process from chemically prepared wood pulp which comprises incorporating in the viscose a mixed ether having the followingformula:

where a: is a whole number from 5 to 25.

13. The improvement in the production of regenerated cellulose productsby the viscose process from chemically prepared wood pulp containing notmore than 0.15% ether extractable matter which is subjected to shreddingwhich comprises adding prior to completion of shredding the alkalicellulose a mixed ether having the following formula:

HI C H:

where :c is a whole number from 5 to 25.

14. The improvement in the production of a regenerated cellulosicproduct from chemically prepared wood pulp by the viscose process whichcomprises adding to the pulp prior to use in the viscose process a mixedether having the following formula:

CH; CH9 onr-o-pnr-o-O-owmmmr (5H1 (3H1 where a: is a whole number from 5to 25. I

PAUL HENRY KENNETH RUSSEl-L GRAY. 1

REFERENCES CITED The following references are of record in the file oithis patent:

UNITED STATES PATENTS

